[patch 20/35 xattr-rework] reiserfs: eliminate per-super xattr lock

From: Jeff Mahoney
Date: Mon Mar 30 2009 - 14:19:26 EST

With the switch to using inode->i_mutex locking during lookups/creation in
the xattr root, the per-super xattr lock is no longer needed.

This patch removes it.

Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
--
fs/reiserfs/inode.c | 14 -------
fs/reiserfs/namei.c | 29 ----------------
fs/reiserfs/super.c | 4 --
fs/reiserfs/xattr.c | 70 +++++++++++++++++++-------------------
fs/reiserfs/xattr_acl.c | 74 ++++++++++++++++++-----------------------
include/linux/reiserfs_fs.h | 3 -
include/linux/reiserfs_fs_sb.h | 3 -
include/linux/reiserfs_xattr.h | 28 ++-------------
8 files changed, 74 insertions(+), 151 deletions(-)

--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -1957,19 +1957,7 @@ int reiserfs_new_inode(struct reiserfs_t
inode->i_nlink = 0;
th->t_trans_id = 0; /* so the caller can't use this handle later */
unlock_new_inode(inode); /* OK to do even if we hadn't locked it */
-
- /* If we were inheriting an ACL, we need to release the lock so that
- * iput doesn't deadlock in reiserfs_delete_xattrs. The locking
- * code really needs to be reworked, but this will take care of it
- * for now. -jeffm */
-#ifdef CONFIG_REISERFS_FS_POSIX_ACL
- if (REISERFS_I(dir)->i_acl_default && !IS_ERR(REISERFS_I(dir)->i_acl_default)) {
- reiserfs_write_unlock_xattrs(dir->i_sb);
- iput(inode);
- reiserfs_write_lock_xattrs(dir->i_sb);
- } else
-#endif
- iput(inode);
+ iput(inode);
return err;
}

--- a/fs/reiserfs/namei.c
+++ b/fs/reiserfs/namei.c
@@ -609,9 +609,6 @@ static int reiserfs_create(struct inode

reiserfs_write_lock(dir->i_sb);

- if (locked)
- reiserfs_write_lock_xattrs(dir->i_sb);
-
retval = journal_begin(&th, dir->i_sb, jbegin_count);
if (retval) {
drop_new_inode(inode);
@@ -624,11 +621,6 @@ static int reiserfs_create(struct inode
if (retval)
goto out_failed;

- if (locked) {
- reiserfs_write_unlock_xattrs(dir->i_sb);
- locked = 0;
- }
-
inode->i_op = &reiserfs_file_inode_operations;
inode->i_fop = &reiserfs_file_operations;
inode->i_mapping->a_ops = &reiserfs_address_space_operations;
@@ -655,8 +647,6 @@ static int reiserfs_create(struct inode
retval = journal_end(&th, dir->i_sb, jbegin_count);

out_failed:
- if (locked)
- reiserfs_write_unlock_xattrs(dir->i_sb);
reiserfs_write_unlock(dir->i_sb);
return retval;
}
@@ -686,9 +676,6 @@ static int reiserfs_mknod(struct inode *

reiserfs_write_lock(dir->i_sb);

- if (locked)
- reiserfs_write_lock_xattrs(dir->i_sb);
-
retval = journal_begin(&th, dir->i_sb, jbegin_count);
if (retval) {
drop_new_inode(inode);
@@ -702,11 +689,6 @@ static int reiserfs_mknod(struct inode *
goto out_failed;
}

- if (locked) {
- reiserfs_write_unlock_xattrs(dir->i_sb);
- locked = 0;
- }
-
inode->i_op = &reiserfs_special_inode_operations;
init_special_inode(inode, inode->i_mode, rdev);

@@ -736,8 +718,6 @@ static int reiserfs_mknod(struct inode *
retval = journal_end(&th, dir->i_sb, jbegin_count);

out_failed:
- if (locked)
- reiserfs_write_unlock_xattrs(dir->i_sb);
reiserfs_write_unlock(dir->i_sb);
return retval;
}
@@ -767,8 +747,6 @@ static int reiserfs_mkdir(struct inode *
locked = reiserfs_cache_default_acl(dir);

reiserfs_write_lock(dir->i_sb);
- if (locked)
- reiserfs_write_lock_xattrs(dir->i_sb);

retval = journal_begin(&th, dir->i_sb, jbegin_count);
if (retval) {
@@ -790,11 +768,6 @@ static int reiserfs_mkdir(struct inode *
goto out_failed;
}

- if (locked) {
- reiserfs_write_unlock_xattrs(dir->i_sb);
- locked = 0;
- }
-
reiserfs_update_inode_transaction(inode);
reiserfs_update_inode_transaction(dir);

@@ -824,8 +797,6 @@ static int reiserfs_mkdir(struct inode *
unlock_new_inode(inode);
retval = journal_end(&th, dir->i_sb, jbegin_count);
out_failed:
- if (locked)
- reiserfs_write_unlock_xattrs(dir->i_sb);
reiserfs_write_unlock(dir->i_sb);
return retval;
}
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -1646,10 +1646,6 @@ static int reiserfs_fill_super(struct su
REISERFS_SB(s)->s_alloc_options.preallocmin = 0;
/* Preallocate by 16 blocks (17-1) at once */
REISERFS_SB(s)->s_alloc_options.preallocsize = 17;
-#ifdef CONFIG_REISERFS_FS_XATTR
- /* Initialize the rwsem for xattr dir */
- init_rwsem(&REISERFS_SB(s)->xattr_dir_sem);
-#endif
/* setup default block allocator options */
reiserfs_init_alloc_options(s);

--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -27,6 +27,12 @@
* these are special cases for filesystem ACLs, they are interpreted by the
* kernel, in addition, they are negatively and positively cached and attached
* to the inode so that unnecessary lookups are avoided.
+ *
+ * Locking works like so:
+ * The xattr root (/.reiserfs_priv/xattrs) is protected by its i_mutex.
+ * The xattr dir (/.reiserfs_priv/xattrs/<oid>.<gen>) is protected by
+ * inode->xattr_sem.
+ * The xattrs themselves are likewise protected by the xattr_sem.
*/

#include <linux/reiserfs_fs.h>
@@ -392,16 +398,17 @@ reiserfs_delete_xattrs_filler(void *buf,
/* This is called w/ inode->i_mutex downed */
int reiserfs_delete_xattrs(struct inode *inode)
{
- struct dentry *dir, *root;
int err = 0;
+ struct dentry *dir, *root;
+ struct reiserfs_transaction_handle th;
+ int blocks = JOURNAL_PER_BALANCE_CNT * 2 + 2 +
+ 4 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb);

/* Skip out, an xattr has no xattrs associated with it */
if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
return 0;

- reiserfs_read_lock_xattrs(inode->i_sb);
dir = open_xa_dir(inode, XATTR_REPLACE);
- reiserfs_read_unlock_xattrs(inode->i_sb);
if (IS_ERR(dir)) {
err = PTR_ERR(dir);
goto out;
@@ -416,18 +423,26 @@ int reiserfs_delete_xattrs(struct inode
if (err)
goto out_dir;

- /* Leftovers besides . and .. -- that's not good. */
- if (dir->d_inode->i_nlink <= 2) {
- root = open_xa_root(inode->i_sb, XATTR_REPLACE);
- reiserfs_write_lock_xattrs(inode->i_sb);
+ /* We start a transaction here to avoid a ABBA situation
+ * between the xattr root's i_mutex and the journal lock.
+ * Inode creation will inherit an ACL, which requires a
+ * lookup. The lookup locks the xattr root i_mutex with a
+ * transaction open. Inode deletion takes teh xattr root
+ * i_mutex to delete the directory and then starts a
+ * transaction inside it. Boom. This doesn't incur much
+ * additional overhead since the reiserfs_rmdir transaction
+ * will just nest inside the outer transaction. */
+ err = journal_begin(&th, inode->i_sb, blocks);
+ if (!err) {
+ int jerror;
+ root = dget(dir->d_parent);
mutex_lock_nested(&root->d_inode->i_mutex, I_MUTEX_XATTR);
err = xattr_rmdir(root->d_inode, dir);
+ jerror = journal_end(&th, inode->i_sb, blocks);
mutex_unlock(&root->d_inode->i_mutex);
- reiserfs_write_unlock_xattrs(inode->i_sb);
dput(root);
- } else {
- reiserfs_warning(inode->i_sb, "jdm-20006",
- "Couldn't remove all entries in directory");
+
+ err = jerror ?: err;
}

out_dir:
@@ -437,6 +452,9 @@ out:
if (!err)
REISERFS_I(inode)->i_flags =
REISERFS_I(inode)->i_flags & ~i_has_xattr_dir;
+ else
+ reiserfs_warning(inode->i_sb, "jdm-20004",
+ "Couldn't remove all xattrs (%d)\n", err);
return err;
}

@@ -485,9 +503,7 @@ int reiserfs_chown_xattrs(struct inode *
if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
return 0;

- reiserfs_read_lock_xattrs(inode->i_sb);
dir = open_xa_dir(inode, XATTR_REPLACE);
- reiserfs_read_unlock_xattrs(inode->i_sb);
if (IS_ERR(dir)) {
if (PTR_ERR(dir) != -ENODATA)
err = PTR_ERR(dir);
@@ -731,6 +747,11 @@ reiserfs_xattr_get(const struct inode *i
goto out;
}

+ /* protect against concurrent access. xattrs are backed by
+ * regular files, but they're not regular files. The updates
+ * must be atomic from the perspective of the user. */
+ mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_XATTR);
+
isize = i_size_read(dentry->d_inode);
REISERFS_I(inode)->i_flags |= i_has_xattr_dir;

@@ -798,6 +819,7 @@ reiserfs_xattr_get(const struct inode *i
}

out_dput:
+ mutex_unlock(&dentry->d_inode->i_mutex);
dput(dentry);

out:
@@ -834,7 +856,6 @@ int reiserfs_xattr_del(struct inode *ino
static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char *);
/*
* Inode operation getxattr()
- * Preliminary locking: we down dentry->d_inode->i_mutex
*/
ssize_t
reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
@@ -848,9 +869,7 @@ reiserfs_getxattr(struct dentry * dentry
return -EOPNOTSUPP;

reiserfs_read_lock_xattr_i(dentry->d_inode);
- reiserfs_read_lock_xattrs(dentry->d_sb);
err = xah->get(dentry->d_inode, name, buffer, size);
- reiserfs_read_unlock_xattrs(dentry->d_sb);
reiserfs_read_unlock_xattr_i(dentry->d_inode);
return err;
}
@@ -866,23 +885,13 @@ reiserfs_setxattr(struct dentry *dentry,
{
struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
int err;
- int lock;

if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

reiserfs_write_lock_xattr_i(dentry->d_inode);
- lock = !has_xattr_dir(dentry->d_inode);
- if (lock)
- reiserfs_write_lock_xattrs(dentry->d_sb);
- else
- reiserfs_read_lock_xattrs(dentry->d_sb);
err = xah->set(dentry->d_inode, name, value, size, flags);
- if (lock)
- reiserfs_write_unlock_xattrs(dentry->d_sb);
- else
- reiserfs_read_unlock_xattrs(dentry->d_sb);
reiserfs_write_unlock_xattr_i(dentry->d_inode);
return err;
}
@@ -902,8 +911,6 @@ int reiserfs_removexattr(struct dentry *
return -EOPNOTSUPP;

reiserfs_write_lock_xattr_i(dentry->d_inode);
- reiserfs_read_lock_xattrs(dentry->d_sb);
-
/* Deletion pre-operation */
if (xah->del) {
err = xah->del(dentry->d_inode, name);
@@ -917,7 +924,6 @@ int reiserfs_removexattr(struct dentry *
mark_inode_dirty(dentry->d_inode);

out:
- reiserfs_read_unlock_xattrs(dentry->d_sb);
reiserfs_write_unlock_xattr_i(dentry->d_inode);
return err;
}
@@ -966,8 +972,6 @@ reiserfs_listxattr_filler(void *buf, con

/*
* Inode operation listxattr()
- *
- * Preliminary locking: we down dentry->d_inode->i_mutex
*/
ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
{
@@ -983,9 +987,7 @@ ssize_t reiserfs_listxattr(struct dentry
return -EOPNOTSUPP;

reiserfs_read_lock_xattr_i(dentry->d_inode);
- reiserfs_read_lock_xattrs(dentry->d_sb);
dir = open_xa_dir(dentry->d_inode, XATTR_REPLACE);
- reiserfs_read_unlock_xattrs(dentry->d_sb);
if (IS_ERR(dir)) {
err = PTR_ERR(dir);
if (err == -ENODATA)
@@ -1114,11 +1116,9 @@ static int reiserfs_check_acl(struct ino
int error = -EAGAIN; /* do regular unix permission checks by default */

reiserfs_read_lock_xattr_i(inode);
- reiserfs_read_lock_xattrs(inode->i_sb);

acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);

- reiserfs_read_unlock_xattrs(inode->i_sb);
reiserfs_read_unlock_xattr_i(inode);

if (acl) {
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -172,6 +172,29 @@ static void *posix_acl_to_disk(const str
return ERR_PTR(-EINVAL);
}

+static inline void iset_acl(struct inode *inode, struct posix_acl **i_acl,
+ struct posix_acl *acl)
+{
+ spin_lock(&inode->i_lock);
+ if (*i_acl != ERR_PTR(-ENODATA))
+ posix_acl_release(*i_acl);
+ *i_acl = posix_acl_dup(acl);
+ spin_unlock(&inode->i_lock);
+}
+
+static inline struct posix_acl *iget_acl(struct inode *inode,
+ struct posix_acl **i_acl)
+{
+ struct posix_acl *acl = ERR_PTR(-ENODATA);
+
+ spin_lock(&inode->i_lock);
+ if (*i_acl != ERR_PTR(-ENODATA))
+ acl = posix_acl_dup(*i_acl);
+ spin_unlock(&inode->i_lock);
+
+ return acl;
+}
+
/*
* Inode operation get_posix_acl().
*
@@ -199,11 +222,11 @@ struct posix_acl *reiserfs_get_acl(struc
return ERR_PTR(-EINVAL);
}

- if (IS_ERR(*p_acl)) {
- if (PTR_ERR(*p_acl) == -ENODATA)
- return NULL;
- } else if (*p_acl != NULL)
- return posix_acl_dup(*p_acl);
+ acl = iget_acl(inode, p_acl);
+ if (acl && !IS_ERR(acl))
+ return acl;
+ else if (PTR_ERR(acl) == -ENODATA)
+ return NULL;

size = reiserfs_xattr_get(inode, name, NULL, 0);
if (size < 0) {
@@ -229,7 +252,7 @@ struct posix_acl *reiserfs_get_acl(struc
} else {
acl = posix_acl_from_disk(value, retval);
if (!IS_ERR(acl))
- *p_acl = posix_acl_dup(acl);
+ iset_acl(inode, p_acl, acl);
}

kfree(value);
@@ -300,16 +323,8 @@ reiserfs_set_acl(struct inode *inode, in

kfree(value);

- if (!error) {
- /* Release the old one */
- if (!IS_ERR(*p_acl) && *p_acl)
- posix_acl_release(*p_acl);
-
- if (acl == NULL)
- *p_acl = ERR_PTR(-ENODATA);
- else
- *p_acl = posix_acl_dup(acl);
- }
+ if (!error)
+ iset_acl(inode, p_acl, acl);

return error;
}
@@ -404,9 +419,7 @@ int reiserfs_cache_default_acl(struct in
if (reiserfs_posixacl(inode->i_sb) && !IS_PRIVATE(inode)) {
struct posix_acl *acl;
reiserfs_read_lock_xattr_i(inode);
- reiserfs_read_lock_xattrs(inode->i_sb);
acl = reiserfs_get_acl(inode, ACL_TYPE_DEFAULT);
- reiserfs_read_unlock_xattrs(inode->i_sb);
reiserfs_read_unlock_xattr_i(inode);
ret = (acl && !IS_ERR(acl));
if (ret)
@@ -429,9 +442,7 @@ int reiserfs_acl_chmod(struct inode *ino
return 0;
}

- reiserfs_read_lock_xattrs(inode->i_sb);
acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);
- reiserfs_read_unlock_xattrs(inode->i_sb);
if (!acl)
return 0;
if (IS_ERR(acl))
@@ -442,17 +453,8 @@ int reiserfs_acl_chmod(struct inode *ino
return -ENOMEM;
error = posix_acl_chmod_masq(clone, inode->i_mode);
if (!error) {
- int lock = !has_xattr_dir(inode);
reiserfs_write_lock_xattr_i(inode);
- if (lock)
- reiserfs_write_lock_xattrs(inode->i_sb);
- else
- reiserfs_read_lock_xattrs(inode->i_sb);
error = reiserfs_set_acl(inode, ACL_TYPE_ACCESS, clone);
- if (lock)
- reiserfs_write_unlock_xattrs(inode->i_sb);
- else
- reiserfs_read_unlock_xattrs(inode->i_sb);
reiserfs_write_unlock_xattr_i(inode);
}
posix_acl_release(clone);
@@ -480,14 +482,9 @@ posix_acl_access_set(struct inode *inode
static int posix_acl_access_del(struct inode *inode, const char *name)
{
struct reiserfs_inode_info *reiserfs_i = REISERFS_I(inode);
- struct posix_acl **acl = &reiserfs_i->i_acl_access;
if (strlen(name) != sizeof(POSIX_ACL_XATTR_ACCESS) - 1)
return -EINVAL;
- if (!IS_ERR(*acl) && *acl) {
- posix_acl_release(*acl);
- *acl = ERR_PTR(-ENODATA);
- }
-
+ iset_acl(inode, &reiserfs_i->i_acl_access, ERR_PTR(-ENODATA));
return 0;
}

@@ -533,14 +530,9 @@ posix_acl_default_set(struct inode *inod
static int posix_acl_default_del(struct inode *inode, const char *name)
{
struct reiserfs_inode_info *reiserfs_i = REISERFS_I(inode);
- struct posix_acl **acl = &reiserfs_i->i_acl_default;
if (strlen(name) != sizeof(POSIX_ACL_XATTR_DEFAULT) - 1)
return -EINVAL;
- if (!IS_ERR(*acl) && *acl) {
- posix_acl_release(*acl);
- *acl = ERR_PTR(-ENODATA);
- }
-
+ iset_acl(inode, &reiserfs_i->i_acl_default, ERR_PTR(-ENODATA));
return 0;
}

--- a/include/linux/reiserfs_fs.h
+++ b/include/linux/reiserfs_fs.h
@@ -2224,7 +2224,4 @@ int reiserfs_unpack(struct inode *inode,
#define reiserfs_write_lock( sb ) lock_kernel()
#define reiserfs_write_unlock( sb ) unlock_kernel()

-/* xattr stuff */
-#define REISERFS_XATTR_DIR_SEM(s) (REISERFS_SB(s)->xattr_dir_sem)
-
#endif /* _LINUX_REISER_FS_H */
--- a/include/linux/reiserfs_fs_sb.h
+++ b/include/linux/reiserfs_fs_sb.h
@@ -403,9 +403,6 @@ struct reiserfs_sb_info {
spinlock_t bitmap_lock; /* this lock on now only used to protect reserved_blocks variable */
struct dentry *priv_root; /* root of /.reiserfs_priv */
struct dentry *xattr_root; /* root of /.reiserfs_priv/.xa */
-#ifdef CONFIG_REISERFS_FS_XATTR
- struct rw_semaphore xattr_dir_sem;
-#endif
int j_errno;
#ifdef CONFIG_QUOTA
char *s_qf_names[MAXQUOTAS];
--- a/include/linux/reiserfs_xattr.h
+++ b/include/linux/reiserfs_xattr.h
@@ -67,45 +67,27 @@ extern struct reiserfs_xattr_handler use
extern struct reiserfs_xattr_handler trusted_handler;
extern struct reiserfs_xattr_handler security_handler;

-static inline void reiserfs_write_lock_xattrs(struct super_block *sb)
-{
- down_write(&REISERFS_XATTR_DIR_SEM(sb));
-}
-static inline void reiserfs_write_unlock_xattrs(struct super_block *sb)
-{
- up_write(&REISERFS_XATTR_DIR_SEM(sb));
-}
-static inline void reiserfs_read_lock_xattrs(struct super_block *sb)
-{
- down_read(&REISERFS_XATTR_DIR_SEM(sb));
-}
-
-static inline void reiserfs_read_unlock_xattrs(struct super_block *sb)
-{
- up_read(&REISERFS_XATTR_DIR_SEM(sb));
-}
-
static inline void reiserfs_write_lock_xattr_i(struct inode *inode)
{
- down_write(&REISERFS_I(inode)->xattr_sem);
+ down_write(&REISERFS_I(inode)->i_xattr_sem);
}
static inline void reiserfs_write_unlock_xattr_i(struct inode *inode)
{
- up_write(&REISERFS_I(inode)->xattr_sem);
+ up_write(&REISERFS_I(inode)->i_xattr_sem);
}
static inline void reiserfs_read_lock_xattr_i(struct inode *inode)
{
- down_read(&REISERFS_I(inode)->xattr_sem);
+ down_read(&REISERFS_I(inode)->i_xattr_sem);
}

static inline void reiserfs_read_unlock_xattr_i(struct inode *inode)
{
- up_read(&REISERFS_I(inode)->xattr_sem);
+ up_read(&REISERFS_I(inode)->i_xattr_sem);
}

static inline void reiserfs_init_xattr_rwsem(struct inode *inode)
{
- init_rwsem(&REISERFS_I(inode)->xattr_sem);
+ init_rwsem(&REISERFS_I(inode)->i_xattr_sem);
}

#else


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